Integrated header connector system

ABSTRACT

Connector assemblies for use with implantable medical devices having easy to assemble contacts is disclosed. The connector assemblies are generally formed by coupling a plurality of contact rings, sealing rings, and spring contact elements together with at least one holding ring to form a connector having a common bore fore receiving a medical lead cable. Contact grooves for positioning the spring contact elements are formed in part by assembling multiple components together.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is an ordinary application claiming priority to provisionalapplication No. 60/911,161, filed Apr. 11, 2007, entitled IntegratedHeader Connector System; and of provisional application No. 61/024,660,filed Jan. 30, 2008, entitled In-Line Connectors; the contents of eachof which are expressly incorporated herein by reference as if set forthin full. This application also expressly incorporates by referenceapplication Ser. No. 12/062,895, filed Apr. 4, 2008, entitled ConnectorAssembly for Use with Medical Devices.

A connector assembly having one or more conductive elements inspaced-apart configuration is generally discussed herein with particulardiscussions extended to connector assemblies for use with implantablemedical devices having easy to assemble contact elements.

BACKGROUND

Implantable medical devices for providing electrical stimulation to bodytissues, for monitoring physiologic conditions, and for providingalternative treatments to drugs are well known in the art. Exemplaryimplantable medical devices include implantable cardio defibrillators,pacemakers, and programmable neurostimulator pulse generators, which arecollectively herein referred to as “implantable medical devices” orIMDs. These IMDs typically incorporate a hermetically sealed deviceenclosing a power source and electronic circuitry. Connected to thesealed housing, also known as a “can”, is a header assembly. The headerassembly includes electrical contact elements that are electricallycoupled to the electronic circuits or to the power source located insidethe can via conductive terminals. The header assembly provides a meansfor electrically communicating via an external medical lead cable,between the electronic circuits or power source located inside thedevice and the actual stimulation point.

Industry wide standards have been adopted for, among other things, thedimensions, size, pin spacing, diameter, etc. for the receptacle and themedical lead cable. Furthermore, good electrical contact must bemaintained during the life of the implantable medical device, and themedical lead cable for use with the IMD must not disconnect from thereceptacle located in the header, yet be detachable for implanting andprogramming purposes and for replacing the IMD when necessary.

Although prior art connector contacts provide viable options for medicaldevice manufacturers, the overall dimensions of existing receptaclespose manufacturing challenges. Among other things, placing stackablerings in between electrically insulating seals and positioningconductive contact elements in between conductive grooves for forming areceptacle and integrating the contact assembly into the IMD aredifficult, costly, and time consuming. Accordingly, there is a need fora receptacle that not only meets the challenges associated withimplantable applications but is also easier to manufacture than avariety of existing receptacles. There is also a need for a receptaclethat is easily adaptable with existing implantable medical devices thatare easier to manufacture than a variety of existing implantable medicaldevices.

SUMMARY

An aspect of the present invention includes an implantable medicaldevice comprising a header attached to a sealed housing; a connectorstack disposed in the header, said header comprising at least two headerhousing sections attached to one another along a seam. A plurality ofgrooves are disposed in the at least two header housing sections and aplurality of dividing walls each separating two adjacent grooves fromone another. A conductive contact ring element having a spring contactelement disposed therein is positioned in a first groove and a sealingring is positioned in a second groove adjacent the conductive contactring element and having the dividing wall positioned therebetween formaintaining the conductive contact ring element and the sealing ring ina spaced apart relationship.

Aspects of the present invention also include a method of assembling aconnector assembly for use with an implantable medical device. Inaccordance with on method, the steps comprise providing a first headersection comprising a plurality of grooves; placing a conductive contactring element into a first groove; placing a sealing ring into a secondgroove; separating the contact ring from the sealing ring with adividing wall; and attaching a second header section to the first headersection.

Another aspect of the present invention is a method for forming aconnector stack having reduced overall length comprising inserting atubular ring into a groove of a header, said groove located between twoseal ring elements, to form a ring groove; providing a spring in saidring groove; and maintaining a space between said tubular ring and saidtwo seal ring elements.

In other embodiments, a method is provided for assembling an implantablemedical connector stack comprising a series of selecting and droppingsteps. The method comprises selecting a first stack component forassembly; dropping the first stack component into a header section;selecting a second stack component for assembly; dropping the secondstack component into the header section; and providing a dividing wall,formed of a material different from the first stack component and thesecond component, in between the first stack component and the secondstack component to maintain the first stack component and the secondstack component in a spaced apart relationship.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded isometric cut-away view of a connector assemblyprovided in accordance with aspects of the present invention, whichcomprises a plurality of seal rings, contact rings, and spring contactelements.

FIG. 2 is an isometric cut-away view of the connector assembly of FIG. 1in an assembled state with a medical lead cable disposed in theconnector bore.

FIG. 3 is an isometric view of the connector assembly of FIG. 2.

FIG. 4 is an isometric transparent view of the connector assembly ofFIGS. 1-3 inside a header and atop a sealed housing of an implantablemedical device.

FIG. 5 is an isometric cut-away transparent view of an alternativeconnector assembly provided in accordance with aspects of the presentinvention usable with an IMD.

FIG. 6 is an isometric view of the alternative connector assembly ofFIG. 5.

FIG. 7 is a cross-sectional side view of the header assembly of theconnector assembly of FIG. 5.

FIG. 8 is an exploded isometric view of the header assembly of theconnector assembly of FIG. 5 with part of the header housing removed forclarity.

FIG. 9 is an isometric view of the connector assembly of FIG. 5assembled in the pre-molded header assembly housing.

FIG. 10 is an isometric view of the IMD of FIG. 5 with part of theheader housing removed for clarity.

FIG. 11 is an isometric view of the IMD of FIG. 5 in a differentperspective and with part of the header housing being displaced to showhow the header housing may be assembled.

FIG. 12 is an isometric view of the IMD of FIG. 5 in a differentperspective.

FIG. 13 is an isometric view of yet another alternative connectorassembly provided in accordance with aspects of the present inventionused with an IMD.

Other aspects and features of the receptacles provided herein may bebetter appreciated as the same become better understood with referenceto the specification and claims.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of the presently preferredembodiments of connector assemblies or stacks for electricallycommunicating with medical leads or conductive terminals. The leads inturn connect to integrated circuits, a power source, and/or circuitchips located inside a sealed medical implantable housing. The connectorassemblies provided in accordance with aspects of the present inventionare not intended to represent the only forms in which the presentinvention may be constructed or utilized. The description sets forth thefeatures and the steps for constructing and using the connectorassemblies of the present invention in connection with the illustratedembodiments. It is to be understood that the same or equivalentfunctions and structures may be accomplished by different embodimentsand are also intended to be encompassed within the spirit and scope ofthe present invention, especially those incorporating a combination offeatures shown in the different embodiments included herein. As denotedelsewhere herein, like element numbers are intended to indicate like orsimilar elements or features.

Referring now to FIG. 1, an exploded isometric cut-away view of aconnector assembly or implantable medical connector stack provided inaccordance with aspects of the present invention is shown, which isgenerally designated 10. The connector assembly 10 is configured toreceive a medical lead cable 12, which has a proximal end 13 comprisinga proximal tip 14, having a recessed section or groove 17 for acceptinga set screw or other lead locking device, and a plurality of electricalterminals 16 interposed in between lead insulators 18. The lead cable 12further comprises a lead body 20 for carrying a plurality of electrodeleads 22 from between the proximal end 13 and a distal end (not shown),which has electrode terminals for providing electrical stimulation tothe body tissues. The number of electrode leads 22 and correspondingnumber of electrical terminals 16 can vary depending on the particularimplant application, which also determines the number of electrical ringcontacts in the connector assembly 10, as further discussed below.Accordingly, applications of the connector assemblies discussed hereininclude unipolar, bipolar, and multi-polar applications by simplychanging the number of components used to make the connector assembly.

In one exemplary embodiment, the connector assembly 10 comprises aplurality of non-conductive seal rings 24, conductive ring contactelements 26, and spring contact elements 28. Together with a holdingring 30, the plurality of seal rings 24, ring contact elements 26, andspring contact elements 28 form the basic components of the connectorassembly 10 of the present embodiment, which has a common bore forreceiving the proximal end of the lead cable 12. Broadly speaking, theseal rings 24 are each configured to seal, along its internal diameter,against the lead cable 12 and, along the outer periphery of its exteriorshoulders, adjacent ring contact element(s) 26. As is readily apparentto a person of ordinary skill in the art, bodily fluids should beprevented from traveling along the lead cable 12 into the connectorassembly or in through the seams between the contact ring element 26 andtwo adjacent seal rings 24. The ring contact elements 26 are eachconfigured to pass an electric signal from a lead 36 located inside anIMD housing to a corresponding spring contact element 28, which thenpasses the electric signal to a corresponding electrical terminal 16 onthe lead cable 12 then onto a corresponding electrode lead 22 locatedinside the lead body 20 and to a corresponding electrode terminal on thedistal end of the lead cable.

In accordance with aspects of the present invention, two sub-classes ofseal rings 24 are incorporated, which include an end seal ring 32 and anintermediate seal ring 34. The end seal ring 32 comprises a singleexternal shoulder 38 for projecting into an adjacent bore 40, whichcould be that of a contact ring 28 or otherwise. The intermediate sealring 34 comprises two external shoulders 38 for projecting into twoadjacent bores 40, which could be that of two different contact rings 28or otherwise, such as one contact ring 28 and a holding ring 30.However, an intermediate seal ring 34 can be used in place of an endseal ring 32 without deviating form the spirit and scope of the presentinvention.

With reference to FIG. 2 in addition to FIG. 1, when two adjacent sealrings 24 engage the bore 40 of a common contact ring element 28, acontact groove 42 is formed for accommodating a spring contact element28. The spring contact element 28, which is preferably a radial or axialcanted coil spring commercially available from Bal Seal Engineering ofFoothill Ranch, Calif., is sized so that it is positioned by the groovealong its two axial ends and establishes contact along its outer andinner radial circumference. Its internal diameter 44 is preferablysmaller than the internal diameter 46 of the seal ring 24, which isslightly smaller than the outer diameter of the proximal end 13 of thelead cable 12. In other words, when the proximal end 13 of the leadcable 12 is inserted into the common bore, the lead cable has a slightinterference fit with the plurality of seal rings 24 and the canted coilspring. The seal rings 24 are also in interference fit with the adjacentbores along their respective external shoulders 38 to facilitateassembly of the various components.

The spring contacts 28 are similarly sized so that each is deflected bythe lead cable 12 to about 5% and up to about 50% of its total radialdeflection with up to about 40% being more preferred. This deflectionrange ensures a sufficient spring contact force is generated between thecontract rings 26 and the electric terminals 16 on the lead cable 12 fortransferring electric signals between the two.

Referring again to FIG. 1, in one exemplary embodiment, the contactrings 26 are each generally cylindrical in configuration. Morepreferably, each contact ring 26 has a generally constant inner diameterand outer diameter with two square ends, with normal manufacturingtolerance being acceptable. Said differently, the contact rings 26 donot have machined or formed grooves for forming contact grooves thereinfor accommodating the spring contact elements 28. The contact rings 26have a simple profile, which in one embodiment is tubular in shape andmakes manufacturing the rings and assembling the spring contacts 28therein easier and therefore more cost effective. The contact groovesare formed instead by a combination of adjacent seal rings 24 and theinner surface of the ring contact element 26. While FIG. 1 is the morepreferred design, alternative contact ring internal geometries arepossible in the area of contact with the spring without compromisingease of assembly for the spring 28 and contact ring. For example, thecontact ring inside diameter can have a “v” shaped groove geometry inthe area of the spring contact so that two points of contact areavailable with the spring versus one.

Other geometries are also contemplated. For example, the contact ring 26may have a thicker section so that there are at least two internaldiameters. The spring contact element 28 can then be inserted throughthe larger internal diameter end of the contact ring 26 until it abutsthe shoulder formed at the intersection between the two differentinternal diameters. Thus, different diameters and undulating internalsurfaces for the contact rings are contemplated. The ring with av-shaped groove can be considered a sub-species of a ring having atleast two internal diameters. Still alternatively, the plurality ofcontact rings in a single connector assembly may vary, i.e., are notuniform. For example, it is possible to use a ring with a “v” shapedgroove at the distal most end of the connector assembly and rings with asmoother contour as shown in FIG. 1 for the remaining contact rings.Still alternatively, a ring with two different internal diameters may beused with the ring having a v-shaped groove and with rings having auniform internal diameter. If a contact ring having two differentinternal diameters at its two ends is used, the seal rings 24 aremodified accordingly to engage the different internal diameters of thecontact ring. Thus, contact rings provided herein not only can have asmooth internal diameter, but also machined surfaces and undulatingsurfaces.

Thus, in accordance with one aspect of the present invention, there isprovided a method for assembling a plurality of components to form aconnector assembly comprising engaging a first seal ring 34 to a holdingring 30, engaging a first contact ring 26 with the first seal ring 34,placing a first spring contact element 28 inside the first contact ring,and engaging a second seal ring 34 with the first contact ring to form aring groove for constraining the first spring contact therein. Themethod further comprises the steps that include adding other seal rings,contact rings, and spring contact elements to form a connector assemblyhaving a desired number of contact grooves. More preferably, the methodfurther comprises the steps of assembling a connector assembly withouthaving to utilize a tool or by hand or by secondary assembly processesmanipulate, compress, bend, or distort a spring contact to fit within acontact groove. The assembled connector assembly is then placed into amold cavity and over-molded with an implantable grade polymer orelastomer, such as epoxy or silicone. The connector assembly can also beinserted into a pre-molded header, which resembles a housing having acavity for receiving the connector assembly and one or more openings forplacing the connector assembly into the pre-molded header. The one ormore openings are then backfilled or sealed, typically after attachingor welding the leads from the sealed housing to the contact rings, tocomplete the assembly.

In accordance with other aspects of the present invention, there isprovided an alternative method for assembling a connector assembly inwhich a dowel or assembly pin (not shown) is used, which resembles theproximal end 13 of the lead cable 12 shown in FIG. 1. The assembly pin(not shown) is used to construct the connector assembly 10 by firstplacing a holding ring 30 on an end of the assembly pin and thensubsequently placing other components on the pin and then sliding theminto engaging with the earlier placed components. The assembledcomponents, i.e., the connector assembly, may then be secured by placingthe same inside a cavity and over-molding the assembly with animplantable grade polymer or elastomer.

In the embodiment shown, the holding ring 30 functions as an end cap andhas an end wall 46 and a shoulder 48 for mating engagement with theshoulder on the seal ring 34. However, a reverse configuration in whichthe holding ring 30, or contact ring 26, projects into the seal ring 24is envisioned, although less preferred. A threaded bore 50 for receivinga set screw 52 is incorporated in the holding ring 30 to more securelyfixing the lead cable 12 to the connector 10 assembly (FIG. 2).Alternatively, an end holding ring (not shown) may be incorporated atthe distal most end 54 of the connector assembly for providing thelocking function on the lead cable 12. During the over-molding step, awindow should be formed around the threaded bore 50 for securing thelead cable, which can then be back-filled using a curable andimplantable material.

Referring again to FIG. 2, the seal rings 24 of the present embodiment,except for the end seal ring 32, are each symmetrical abound acenterline drawn perpendicular to the axis defined by the lead cable 12and through the center of the seal ring. However, non-symmetry or otherconfigurations are possible so long as a contact groove foraccommodating a spring contact is formed at least in part by engagingthe contact ring 26 with two adjacent seal rings 24. Furthermore, whilethe seal rings 24 of the present embodiment are shown each comprising aninternal projection for sealing against the lead cable 12, as previouslydiscussed, two or more projections may be incorporated without deviatingfrom the spirit and scope of the present invention. Still furthermore,part of the seal ring that projects into the bore of a contact ring canbe made separately. In other words, a seal ring may be made byco-molding over over-molding two separate components.

Following assembly of the various components to form the connectorassembly 10 shown in FIG. 2, the connector assembly is encased inside animplantable elastomer or polymer layer, as previously discussed. Theconnector assembly 10 is preferably molded with an assembly pin locatedinside the common bore to ensure alignment, both radially and axially,of the various connector components. The encased connector may bereferred to as a connector header, for placing on a can or sealedhousing of an IMD. In one exemplary embodiment, windows (not shown) areleft exposed through the over-molded layer adjacent each contact ring26. When the header is placed over the can, a plurality of contact leads35 in communication with a power source and/or electronic circuitsinside the can project upwardly into physical contact with the contactrings 26. The contact leads 36 may then welded to a correspondingcontact ring 26 to ensure good electrical contact through the windows.The windows are then backfilled and sealed using curable implantableelastomer or polymer.

FIG. 3 is fully assembled view of the connector assembly 10 of FIGS. 1and 2 with the medical lead cable 12 disposed inside the common bore. Ascan be appreciated, the connector stack 10 provided herein allows forthe distance between one ring contact element and an adjacent ringcontact element to be reduced. The reduction is facilitated by, amongother things, eliminating metallic side walls for capturing the springsinside the ring grooves. Thus, the overall length of the stack, from theholding ring 30 to the distal end most seal element 24, may be reducedcompared to connector stacks having metallic or conductive side wallsfor capturing the springs. Accordingly, a method is provided for forminga connector stack having reduced overall length comprising inserting atubular ring into a groove between two seal ring elements to form a ringgroove, and providing a spring in said ring groove. Advantageously, thestack provided in accordance with aspects of the present inventionreduces manufacturing and installation costs, simplifies assembly, andshortens the overall length of the stack to allow for smaller sizedIMDs.

Referring now to FIG. 4, an IMD 56 incorporating a connector assembly 10provided in accordance with aspects of the present invention is shown.The connector assembly 10 is shown in a header 58, which is shown as atransparent material or structure for purposes of discussion. Inpractice, the overcoat or over-molding layer is more commonlysemi-opaque. The header 58 is situated over a can 60, which ishermetically sealed with a power source, electronic circuits. Aspreviously discussed, the IMD can be any one of plurality of IMDs formedical treatment, monitoring, or diagnostics.

Also shown in FIG. 4 are weld traces 62 for welding the leads 36 to thecontact rings 26. Typically, the leads 36 project through one or morefeed through terminals that pass through the hermetically sealed housingor can 60 to contact the contact rings 26. Although a single connectorassembly 10 is shown inside the header 58, two or more connectorassemblies 10 may be used if desired depending on the particular implantapplication. The connector assemblies may be stacked side-by-side or ontop of one another.

FIG. 5 is a an isometric cut-away transparent view of an alternativeconnector assembly 100 provided in accordance with aspects of thepresent invention for use with an IMD 102. The present connectorassembly 100 is configured to be assembled to a pre-formed headerhousing 104. In one aspect of the present invention, the header housing104 comprises two housing sections 106 a, 106 b each formed with aplurality of cavities or grooves 108, 110, 112. The grooves are eachspaced apart from one another by a dividing wall 114. Furthermore, eachgroove is configured to accommodate or accept a specific connectorcomponent. Accordingly, there is provided a holding ring groove 108, asealing ring groove 110, and a contact ring groove 112.

The grooves are each sized to snuggly receive a connector component.Moreover, they are sized and aligned so that when the various connectorcomponents are mounted therein, the bores of the various componentsalign. More preferably, the grooves are aligned to provide a generallyuniform longitudinal axis among the various connector components todefine a common bore.

FIG. 6 is an isometric view of the alternative connector assembly ofFIG. 5 in a fully assembled position. As can be appreciated, theconnector stack 100 provided herein allows for select and dropinstallation. That is, the connector stack 100 may be assembled by pickand choosing the proper component and dropping that component into aproper groove. For example, a ring and spring combination will bedropped into a contact ring groove and a sealing ring element is to bedropped into a sealing ring groove to assemble the stack. Accordingly, amethod is provided for assembling an implantable medical connector stackcomprising selecting a first stack component for assembly; dropping thefirst stack component into a header section; selecting a second stackcomponent for assembly; dropping the second stack component into theheader section; and providing a wall, formed of a material differentfrom the first stack component and the second component, in between thefirst stack component and the second stack component to maintain thefirst stack component and the second stack component in a spaced apartrelationship. In another aspect of the present invention, a canted coilspring is placed inside the first stack component or the second stackcomponent before placement of said stack component into the headersection. In another embodiment, the wall is singularly formed with theheader section, preferably made from an polymer or elastomer material,such as epoxy or silicone.

FIG. 7 is a cross-sectional side view of the connector assembly 100located inside the header housing 104. As shown, a first contact ring26, having a spring contact element 28 positioned therein, is positionedin a first groove 112. A sealing ring 104 is positioned in a secondgroove 110. A second contact ring 26 and spring contact element 28 arepositioned in a third groove 112. A second sealing ring 116 ispositioned in a fourth groove 110 and so forth. The connector assembly100 may have as few as one contact ring 26 and as many as necessary toperform the needed tasks for a particular IMD application. In theembodiment shown, a third contact ring 26 having a spring contactelement 28 is positioned in a fifth groove 112. A holding ring 30comprising a threaded bore for cooperating with a set screw ispositioned in the seventh groove 108. In one embodiment, the outsidediameter (OD) of the sealing ring 116 and the OD of the ring contactelement 26 is about the same. More preferably, the OD of the sealingring 116 is smaller than the OD of the ring contact element 26.

As can be appreciated, a feature of the present embodiment is aplurality of header walls 114 located in between alternating pairs ofring contact elements 26 and sealing rings 116 to keep the stackcomponents in spaced apart relationships, except for the springs 28 andthe ring contact elements 26, which are always in electricalcommunication with one another. In another aspect of the invention, amethod is provided for forming ring grooves for retaining canted coilsprings in the absence of conductive side walls. The method comprisingplacing a first ring contact element into a first groove of a header andforming a ring groove from a bottom wall of the ring contact element andtwo header walls. The method further comprising placing a dielectricseal element into a second groove, spaced apart from the first groove,and placing a second ring contact element into a third groove, which isspaced apart from the second groove and the first groove.

As is readily apparent to a person of ordinary skill in the art, eachcontact ring 26 is isolated from an adjacent contact ring by a sealingring 116 and at least one dividing wall 114. The sealing rings are eachpreferably generally ring shape (FIG. 8) and comprises a bevel innercircumference or opening for sealing engagement with a medical leadcable.

FIG. 8 is an exploded isometric view of the header assembly or stack 100of FIG. 5 with part of the header housing 104 removed for clarity. Theconnector assembly may be assembled into a header housing 104 by firstinserting the various connector components into the plurality of groovesinside a first housing section 106 a. As discussed above, the groovesare pre-formed into the two housing sections 106 a, 106 b. Theembodiment shown allows for easy installation by simply inserting theplurality of connector components or stack components, i.e., ringcontact elements, seal ring elements, canted coil springs, and one ormore holding rings, into a matching groove, i.e., having matchingdimensions and/or geometries for accommodating the corresponding stackcomponents. To provide for more accurate alignment, an assembly pin 118(FIG. 9) is preferably inserted into the common or aligned bore beforecoupling the second housing section 106 b with the first housingsection, which are then glued or bonded together using any known priorart methods. In an alternative embodiment, a plurality of windows may beprovided in the two housing sections 106 a, 106 b to back-fill withcurable implantable elastomer or polymer to maintain alignment. Thecurable material flows into the crevices to hold the various componentsin alignment even after the assembly pin is removed.

FIG. 10 is an isometric view of the IMD of FIG. 5 with part of theheader housing 104 removed for clarity. As shown, contact leads 36 fromthe sealed housing 60 are welded to the contact rings 26 prior tocoupling the second housing section 106 b with the first housing section106 a (FIG. 11). A window 120, which can be back-filled with curablematerial, is provided for manipulating a set screw. In one aspect of thepresent invention, a beveled section may be provided along the seam ofthe two housing sections 106 a, 106 b for facilitating assembly of thetwo housing sections.

FIG. 12 is an isometric view of the IMD of FIG. 5 in a differentperspective. FIG. 12 shows the assembly pin removed and a medical leadcable 12 coupled to the connector assembly.

FIG. 13 is a isometric view of yet another alternative connectorassembly 122 provided in accordance with aspects of the presentinvention for use with an IMD. In the present alternative connectorassembly 122, the holding ring 30 has been moved to the proximal end ofthe connector assembly.

Although limited preferred embodiments and methods for making and usingconnector assemblies provided in accordance with aspects of the presentinvention have been specifically described and illustrated, manymodifications and variations will be apparent to those skilled in theart. For example, various material changes may be used, incorporatingdifferent mechanical engagement means to attach the various componentsto one another, making use of two or more different materials orcomposites, making a sealing ring from multiple pieces rather than asingularly molded piece, etc. Accordingly, it is to be understood thatthe connector assemblies constructed according to principles of thisinvention may be embodied in other than as specifically describedherein. The invention is also defined in the following claims.

1. An implantable medical device comprising a header attached to asealed housing; a connector stack disposed in the header, said headercomprising at least two header housing sections attached to one anotheralong a seam; a plurality of grooves disposed in the at least two headerhousing sections; a plurality of dividing walls each separating twoadjacent grooves from one another; a conductive contact ring elementhaving a spring contact element disposed therein positioned in a firstgroove; a sealing ring positioned in a second groove adjacent theconductive contact ring element and having the dividing wall positionedtherebetween for maintaining the conductive contact ring element and thesealing ring in a spaced apart relationship.
 2. The implantable medicaldevice of claim 1, further comprising a second conductive contact ringelement positioned in a third groove, which is spaced apart from thesecond groove and the first groove.
 3. The implantable medical device ofclaim 1, wherein the spring contact element is a radial canted coilspring.
 4. The implantable medical device of claim 1, wherein the headerhousing, the conductive contact ring element, and the sealing ring havea common bore.
 5. The implantable medical device of claim 1, wherein thesealed housing is part of a implantable pulse generator.
 6. Theimplantable medical device of claim 1, further comprising a holding ringcomprising a set screw positioned in one of the plurality of grooves. 7.The implantable medical device of claim 6, further comprising a cut-outon the header for accessing the set screw.
 8. A method of assembling aconnector assembly for use with an implantable medical devicecomprising: providing a first header section comprising a plurality ofgrooves; placing a conductive contact ring element into a first groove;placing a sealing ring into a second groove; separating the contact ringfrom the sealing ring with a dividing wall; and attaching a secondheader section to the first header section.
 9. The method of claim 8,further comprising placing a second conductive contact ring element intoa third groove, which is spaced apart from the second groove and thefirst groove before attaching the second header section to the firstheader section.
 10. The method of claim 9, further comprising placing aspring contact element in each of the conductive ring contact elementand the second conductive contact ring element before attaching thesecond header section to the first header section.
 11. The method ofclaim 10, further comprising placing a second sealing ring into a fourthgroove before attaching the second header section to the first headersection.
 12. The method of claim 8, further comprising placing anassembly rod in through the conductive ring contact element beforeplacing the conductive ring contact element into the first groove. 13.The method of claim 8, wherein the header comprises an opening foraccessing a common bore of the connector stack.
 14. A method for forminga connector stack having reduced overall length comprising inserting atubular ring into a groove of a header, said groove located between twoseal ring elements, to form a ring groove; providing a spring in saidring groove; and maintaining a space between said tubular ring and saidtwo seal ring elements.
 15. The method of claim 14, wherein said tubularring has a bottom wall and no side walls.
 16. The method of claim 14,further comprising placing a second tubular ring into a groove locatedadjacent one of the two seal ring elements.
 17. The method of claim 16,wherein the second tubular ring is separated from one of the two sealring elements by a dividing wall.
 18. The method of claim 14, furthercomprising placing a holding ring into a groove.
 19. A method isprovided for assembling an implantable medical connector stackcomprising selecting a first stack component for assembly; dropping thefirst stack component into a header section; selecting a second stackcomponent for assembly; dropping the second stack component into theheader section; and providing a dividing wall, formed of a materialdifferent from the first stack component and the second component, inbetween the first stack component and the second stack component tomaintain the first stack component and the second stack component in aspaced apart relationship.
 20. The method of claim 19, furthercomprising dropping a holding ring into a groove of the header section.21. The method of claim 19, further comprising attaching a second headersection to the header section.
 22. The method of claim 21, furthercomprising attaching the header section and the second header section toa sealed housing of an implantable medical device.